1. Field of the Invention
The present invention relates to an improvement in a one-step permanent wave solution.
2. State of the Art
Among permanent wave solutions heretofore known, wave solutions of a two-step type have been employed for about forty years. A two-step type permanent wave solution comprises a first solution which practically contains ammonium thioglycolate as a main component, to which a caustic alkali or an alkali carbonate is added, and a second solution which is practically an aqueous solution of alkali bromate. According to the widely believed waving theory, permanent waving is carried out in the following manner: by applying the first solution to hair, the sulfur bond (--S--S--) of cystine contained in keratin which constitutes hair is cut off (--S--H H--S--) by means of hydrogenation, thereby softening the hair into a condition wherein it is curled or strained, and then by applying the second solution to the hair, the cut off bond is recovered by oxidation (--S--H H--S--+O.sub.2 .fwdarw.--S--S--+H.sub.2 O) so as to fix the curls in the hair. Since a conventional permanent wave solution comprises a first solution which contains alkali (alkali carbonate, caustic alkali, or ammonia) to such an excessive degree that the first solution has alkalinity (i.e. the quantity, in terms of ml., of 0.1N-HCl which is required for neutralizing 1 ml. of the relevant alkali) of more than 3.5, when hair is coated with the first solution, a cyanide (e.g. potassium cyanide) is immediately produced. The cyanide acts to cut off the sulfur bond (--S--S--) of cystine. More specifically, a reaction between cystine (R--S--S--R, R representing keratine) and potassium cyanide (KCN) occurs in two steps as shown in the following chemical formulas (i) and (ii): EQU R--S--S--R+KCN.revreaction.R--S--CN+K--S--R (i) EQU R--S--CN+K--S--R.revreaction.R--S--R+K--S--CN (ii)
As shown above, lanthionine R--S--R and potassium thiocyanide are produced by this reaction ["CHEMICAL AND PHYSICAL BEHAVIOR OF HUMAN HAIR" by C. R. Robbins, Page 56, published by Fragrance Journal in 1982]. Then, as shown in the following chemical formula (iii), thiocyanate (--SCN) is oxidized with oxidizing agent, a main component of the second solution, alkali bromate, if the second solution is used, or by red prussiate (ferricyanide) which is a by-product in the waste liquid of the permanent wave solution even if the second solution is not used. As a result of the oxidation, cyanides are produced. EQU --SCN+O.sub.2 .fwdarw.--CN+SO.sub.2 (iii)
Meanwhile, lanthionine R--S--R remains in the hair, and when lanthionine is fixed, the hair is supposed to be permanently waved.
After various studies, the inventor has found it quite erroneous to consider, as in the conventional waving theory, that permanent waving is carried out by cutting off the sulfur bond of cystine by means of hydrogenation with a mercaptan, and by recovering the cut off sulfur bond by means of oxidation thereof. Instead, the inventor has found it correct to consider that permanent waving is carried out, on application of the conventional two-step type wave solution, in the steps expressed by the above chemical formulas (i) to (iii), cutting off the sulfur bond with the cyanide and recovery of the cut off sulfur bond by means of oxidation.
As stated above, cyanides are produced, when the first solution is applied to the hair, due to decomposition of keratine by the mercaptan which is the main component of the first solution and the alkali. Cyanides themselves are, as widely known, strong poisons, and further, they react with iron in hair to form hexacyano ferrous- or ferric- compounds (yellow or red prussiates), which further react with iron ions in the blood to become more poisonous than the cyanides, thus causing not only damaged hair and falling hair, but also anemia and cancer, and having a harmful effect on pregnant women (or embryos). Further, thiocyanate remaining in the hair can react with water when the hair is shampooed to produce cyanides, thus causing decomposition of hair and a short duration of the permanent waving effect of only one to two months, while leaving the hair damaged and removed of curls.
The above finding of the biochemical facts by the inventor is the basis of the presently proposed invention concerning the improved permanent wave solution.
The inventor has made studies in order to achieve permanent waving which is capable of producing the waving effect with ease, and also of improving the durability of permanently waved curls, and has already proposed a one-step permanent wave solution as well as a method of preparing an improved one-step wave solution, as disclosed in Japanese Pat. No. 730927 and U.S. Pat. No. 4,192,863.
The improved one-step permanent wave solution prepared by the method which the inventor previously proposed has the following chemical composition (in weight %):
ammonium thioglycolate: 2 to 5%;
caustic potash or caustic soda: not more than 0.1%;
oxy-organic acid: 0.1 to 0.5%;
ethyl alcohol: 0.01 to 30%
28% ammonia water: not more than 2.4%;
monoethanolamine, diethanolamine, or triethanolamine: 0.005 to 1.0%; and
distilled water as the remainder,
pH of said solution being adjusted to 7.0 to 9.6.
The improved one-step permanent wave solution can be used in beauty parlors as follows:
(1) The hair is wound on a plurality of rods and fastened with rubber bands while coating the wound hair with 50 ml. of the permanent wave solution in about 20 minutes;
(2) The head of the user is covered with a cap for about 10 to 20 minutes, and then the cap is removed; and
(3) The hair as wound is rinsed with warm water, and after a lapse of a few minutes, the rods are removed from the hair. The setting is then completed by combing the hair under using a hand dryer while taking advantage of residual moisture in the hair. If desired, all or a part of the hair may be re-wound on rollers having relatively larger diameters (e.g. 1 to 2 cm) than the rods, and then dried by applying thereto hot air of about 50.degree. to 60.degree. C. for about 15 minutes, so as to produce large curls. Even after washing, the large curls maintain substantially to the same diameters as those of the rollers.
According to the findings of the inventor, by using the above one-step permanent wave solution, permanent waving is carried out by a combination of hydrolysis of the sulfur bond of cystine (--S--S--+H.sub.2 O--S--OH H--S--) and subsequent recovering of the sulfur bond by means of dehydration.
In conducting permanent waving, curtailment of the overall time required and improvement in durability of the waving effect are the things that should be pursued consistently. Further, in applying permanent wave solutions, it is an important problem to eliminate the poisonous effect of cyanides and hexacyano ferrous or ferric compounds.